Studies will be performed to measure intracellular flux rates of the tricarboxylic acid cycle, the glyoxylate cycle, glyconeogenesis, and lipogenesis in the ciliated protozoan Tetrahymena pyriformis. Data will be obtained from experiments using (1-C14)-labeled substrates and will be interpreted according to the three-pools of acetyl CoA model recently published for the structure of intermediate metabolism in this organism. The effect of reduced oxygen tension on the supply of glyconeogenic precursors from the peroxisomal and from the mitochondrial compartments will be determined, and the time course of recovery of metabolic pathways from partial anaerobiosis will be investigated. Studies will also be performed to establish the relative effects of 4-pentenoic acid on glyconeogenesis from the peroxisomal and mitochondrial compartments, as well as the effect of 4-pentenoic acid on the rate of lipogenesis. The role of the pentose cyclic enzymes in gluconeogenesis in Tetrahymena will be explored, and the amount and localization of these enzymes will be established.